U.S. patent number 10,610,889 [Application Number 15/746,136] was granted by the patent office on 2020-04-07 for multi-layer coating film formation method.
This patent grant is currently assigned to KANSAI PAINT CO., LTD.. The grantee listed for this patent is KANSAI PAINT CO., LTD.. Invention is credited to Masayuki Itoh, Tatsuo Kuramochi, Kenichiro Matsunaga, Nobuhiko Narita, Yosuke Toyoda.
United States Patent |
10,610,889 |
Itoh , et al. |
April 7, 2020 |
Multi-layer coating film formation method
Abstract
The present invention relates to a method for forming a
multilayer coating film, the method comprising sequentially
applying a colored coating composition (X), an effect pigment
dispersion (Y), and a clear coating composition (Z) to a substrate
to form an uncured colored coating film, an uncured effect coating
film, and an uncured clear coating film, respectively, and heating
the uncured colored coating film, the uncured effect coating film,
and the uncured clear coating film to simultaneously cure these
three coating films, thereby forming a multilayer coating film;
wherein the effect pigment dispersion (Y) contains water, a
specific surface modifier (A), a flake-effect pigment (B), and a
viscosity modifier (C); and a film obtained by applying the effect
pigment dispersion (Y) to a dry film thickness of 0.2 .mu.m has a
light transmittance at a wavelength of 550 nm of 10 to 50%.
Inventors: |
Itoh; Masayuki (Aichi,
JP), Matsunaga; Kenichiro (Kanagawa, JP),
Toyoda; Yosuke (Kanagawa, JP), Kuramochi; Tatsuo
(Kanagawa, JP), Narita; Nobuhiko (Kanagawa,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
KANSAI PAINT CO., LTD. |
Hyogo |
N/A |
JP |
|
|
Assignee: |
KANSAI PAINT CO., LTD. (Hyogo,
JP)
|
Family
ID: |
57943078 |
Appl.
No.: |
15/746,136 |
Filed: |
July 29, 2016 |
PCT
Filed: |
July 29, 2016 |
PCT No.: |
PCT/JP2016/072451 |
371(c)(1),(2),(4) Date: |
January 19, 2018 |
PCT
Pub. No.: |
WO2017/022698 |
PCT
Pub. Date: |
February 09, 2017 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
|
US 20180214912 A1 |
Aug 2, 2018 |
|
Foreign Application Priority Data
|
|
|
|
|
Jul 31, 2015 [JP] |
|
|
2015-151682 |
Mar 11, 2016 [JP] |
|
|
2016-048602 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09D
201/00 (20130101); B05D 7/57 (20130101); C09D
133/02 (20130101); B05D 7/14 (20130101); B05D
7/572 (20130101); B05D 1/36 (20130101); B05D
5/067 (20130101); C09D 7/62 (20180101); C09D
5/36 (20130101); B05D 5/061 (20130101); B05D
3/007 (20130101); B05D 7/574 (20130101); C08K
9/02 (20130101); B05D 2201/00 (20130101); B05D
2202/10 (20130101) |
Current International
Class: |
B05D
7/00 (20060101); B05D 7/14 (20060101); C09D
201/00 (20060101); B05D 5/06 (20060101); B05D
1/36 (20060101); C09D 5/36 (20060101); C09D
7/62 (20180101); C09D 133/02 (20060101); B05D
3/00 (20060101); C08K 9/02 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
3 030 637 |
|
Jan 2018 |
|
CA |
|
63-272544 |
|
Nov 1988 |
|
JP |
|
11-90318 |
|
Apr 1999 |
|
JP |
|
2003-313500 |
|
Nov 2003 |
|
JP |
|
2005-120249 |
|
May 2005 |
|
JP |
|
2006-95522 |
|
Apr 2006 |
|
JP |
|
2009-28690 |
|
Feb 2009 |
|
JP |
|
2009-28693 |
|
Feb 2009 |
|
JP |
|
2009-155537 |
|
Jul 2009 |
|
JP |
|
2014-4552 |
|
Jan 2014 |
|
JP |
|
2014-51628 |
|
Mar 2014 |
|
JP |
|
2014-169434 |
|
Sep 2014 |
|
JP |
|
2015-51385 |
|
Mar 2015 |
|
JP |
|
5685044 |
|
Mar 2015 |
|
JP |
|
2004/105965 |
|
Dec 2004 |
|
WO |
|
2009/157588 |
|
Dec 2009 |
|
WO |
|
2014/024884 |
|
Feb 2014 |
|
WO |
|
2014/119781 |
|
Aug 2017 |
|
WO |
|
2013/012014 |
|
Jan 2018 |
|
WO |
|
Other References
International Search Report dated Oct. 25, 2016 in International
(PCT) Application No. PCT/JP2016/072451. cited by applicant .
International Preliminary Report on Patentability dated Nov. 9,
2017 in International (PCT) Application No. PCT/JP2016/072451.
cited by applicant .
Extended European Search Report dated Mar. 22. 2019 in
corresponding European Patent Application No. 16832977.9. cited by
applicant.
|
Primary Examiner: Tschen; Francisco W
Attorney, Agent or Firm: Wenderoth, Lind & Ponack,
L.L.P.
Claims
The invention claimed is:
1. A method for forming a multilayer coating film by sequentially
performing the following steps (1) to (4): (1) applying a colored
coating composition (X) to a substrate to form a colored coating
film, (2) applying an effect pigment dispersion (Y) to the colored
coating film formed in step (1) to form an effect coating film, (3)
applying a clear coating composition (Z) to the effect coating film
formed in step (2) to form a clear coating film, and (4) heating
the uncured colored coating film, the uncured effect coating film,
and the uncured clear coating film formed respectively in steps (1)
to (3) to simultaneously cure these three coating films; wherein:
the effect pigment dispersion (Y) contains a base resin, water, a
surface modifier (A), a flake-effect pigment (B), a viscosity
modifier (C), and optionally at least one crosslinkable component
(D), wherein a ratio of the flake-effect pigment (B) to the total
amount of the base resin and the crosslinkable component (D) is
within a range of 4/3 to 100/1, based on the solids content mass,
as calculated based on the following formula: 4/3 to
100/1=flake-effect pigment (B)/(base resin+crosslinkable component
(D)), a solids content of the effect pigment dispersion (Y) during
coating is 0.1 to 15.0 mass %, the surface modifier (A) has a
contact angle of 8 to 20.degree. with respect to a previously
degreased tin plate, the contact angle being measured in such a
manner that a liquid that is a mixture of isopropanol, water, and
the surface modifier (A) at a ratio of 4.5/95/1 is adjusted to have
a viscosity of 150 mPas measured by a B-type viscometer at a rotor
rotational speed of 60 rpm at a temperature of 20.degree. C., 10
.mu.L of the liquid is added dropwise to the tin plate, and the
contact angle with respect to the tin plate is measured 10 seconds
after dropping, a film obtained by applying the effect pigment
dispersion (Y) to a dry film thickness of 0.2 .mu.m has a light
transmittance at a wavelength of 550 nm of 10 to 50%, and the
effect coating film has a dry film thickness of 0.01 to 4.0
.mu.m.
2. The method for forming a multilayer coating film according to
claim 1, wherein the clear coating composition (Z) is a
one-component clear coating composition; and the effect pigment
dispersion (Y) and/or the clear coating composition (Z) contains
the at least one crosslinkable component (D), wherein the at least
one crosslinkable component (D) is selected from the group
consisting of melamine, a melamine derivative, (meth)acrylamide, an
N-methylol group- or N-alkoxymethyl group-containing
(meth)acrylamide copolymer, and a blocked or unblocked
polyisocyanate compound, wherein: when the effect pigment
dispersion (Y) contains the crosslinkable component (D), the
content thereof as a solids content is within a range of 10 to 100
parts by mass based on 100 parts by mass of the solids content of
the effect pigment in the effect pigment dispersion (Y), and when
the clear coating composition (Z) contains the crosslinkable
component (D), the content thereof as a solids content is within a
range of 5 to 25 parts by mass based on 100 parts by mass of the
resin solids content of the clear coating composition (Z).
3. The method for forming a multilayer coating film according to
claim 1, wherein the clear coating composition (Z) is a
two-component clear coating composition containing a
hydroxy-containing resin and a polyisocyanate compound.
4. The method for forming a multilayer coating film according to
claim 1, wherein the effect pigment dispersion (Y) has a viscosity
(B60) of 60 to 1500 mPas measured using a B-type viscometer at a
rotor rotational speed of 60 rpm at a temperature of 20.degree.
C.
5. The method for forming a multilayer coating film according to
claim 1, wherein the surface modifier (A) is a silicone-based
surface modifier.
6. The method for forming a multilayer coating film according to
claim 1, wherein the surface modifier (A) has a dynamic surface
tension of 50 to 70 mN/m.
7. The method for forming a multilayer coating film according to
claim 1, wherein the flake-effect pigment (B) is contained in the
effect pigment dispersion (Y) in an amount of 0.05 to 3.0 parts by
mass, based on 100 parts by mass of the total amount of water, the
surface modifier (A), the flake-effect pigment (B), and the
viscosity modifier (C).
8. The method for forming a multilayer coating film according to
claim 1, wherein the effect coating film has a dry film thickness
of 0.01 to 1.0 .mu.m.
9. The method for forming a multilayer coating film according to
claim 1, wherein the clear coating composition (Z) contains a
carboxy-containing resin and an epoxy-containing resin.
10. The method for forming a multilayer coating film according to
claim 1, wherein the clear coating composition (Z) contains a
hydroxy-containing resin and a melamine resin.
11. The method for forming a multilayer coating film according to
claim 1, wherein the water is contained in the effect pigment
dispersion (Y) in an amount of 70 to 99 parts by mass, and the
flake-effect pigment (B) is contained in the effect pigment
dispersion (Y) in an amount of 0.05 to 3.0 parts by mass based on
100 parts by mass of the total amount of water, the surface
modifier (A), the flake-effect pigment (B), and the viscosity
modifier (C).
12. The method for forming a multilayer coating film according to
claim 1, wherein the base resin is acrylic resin, polyester resin,
alkyd resin or urethane resin.
Description
CROSS-REFERENCE TO RELATED APPLICATION
The present application claims priority to Japanese Patent
Application No. 2015-151682 filed on Jul. 31, 2015, and Japanese
Patent Application No. 2016-048602 filed on Mar. 11, 2016, the
entire contents of which are incorporated herein by reference.
TECHNICAL FIELD
Technical Field
The present invention relates to a method for forming a multilayer
coating film.
Background Art
The purpose of applying coating compositions is mainly to protect
materials and impart an excellent appearance. For industrial
products, excellent appearance, particularly "texture," is
important in terms of enhancing their product power. Although there
are various textures for industrial products desired by consumers,
luster like metal or pearl (hereinafter referred to as "metallic
luster") has recently been desired in the field of automobile
exterior panels, automobile components, home electronics, and the
like.
Metallic luster is a texture characterized in that the surface has
no graininess, like a mirror-finished surface, in that the coated
plate looks shiny when viewed nearly perpendicular to the coated
plate (highlight), and in that, conversely, the coated plate looks
dark when viewed obliquely to the coated plate (shade). That is,
there is a large luminance difference between the highlight region
and the shade region.
Techniques to impart metallic luster to the surface of industrial
products include metal plating treatment, metal deposition
treatment (e.g., PTL 1), and the like. If metallic luster can be
imparted by coating, it is advantageous in terms of ease, cost, and
the like.
PTL 2 discloses a method for forming a metallic coating film, the
method comprising applying a composition comprising non-leafing
aluminum flakes and an organic solvent to an uncured coating
surface, and then applying a clear coating composition.
PTL 3 discloses a metallic coating composition prepared by diluting
a metallic coating material base containing an effect material, a
resin-containing non-volatile solid, and a solvent with a diluent
comprising a high-boiling solvent and a low-boiling solvent at a
dilution rate of 150 to 500%, and adding 5 to 10 parts by weight of
viscous resin based on 100 parts by weight of the resin content in
the metallic coating material base.
PTL 4 discloses a metallic coating composition prepared by diluting
a coating material base comprising, on a solid basis, 10 to 30% of
an effect material, 10 to 50% of a cellulose acetate butyrate resin
having a molecular weight of 25,000 to 50,000 (MWn), and an acrylic
melamine resin as a balance, with an ester-based solvent and/or a
ketone-based solvent at a dilution rate in which the solids content
is 1 to 10 wt. %.
PTL 5 discloses a method for forming a multilayer coating film, the
method using an effect material-containing base coating composition
comprising colloidal particles containing precious metal and/or
metal, and further comprising a coating film-forming resin and a
specific mixed solvent.
PTL 6 discloses a method for forming a multilayer coating film, the
method using a specific effect material-containing base coating
composition comprising a coating film-forming resin and colloidal
particles containing precious metal and/or metal, and the method
being used in combination with a specific coating method.
The coating compositions disclosed in PTL 2 to PTL 6 are
solvent-based coating compositions. However, in terms of low
environmental impact, aqueous coating compositions have recently
been required in the field of metallic coating compositions.
PTL 7 discloses an aqueous base coating composition comprising an
effect pigment composed of metal flakes obtained by crushing a
vapor-deposition metal film, and an aqueous cellulose derivative
having an acid value of 20 to 150 mgKOH/g (solids content), wherein
the aqueous cellulose derivative serves as a main binder resin, and
the content of the effect pigment is 20 to 70 mass % as PWC.
However, a coating film formed from the coating composition
disclosed in PTL 7 had insufficient metallic luster. Further, there
is a cost problem because the use of a binder resin is
essential.
PTL 8 discloses a method for coating an aqueous base coating
composition comprising a flake-effect pigment, the method
comprising applying an aqueous base coating composition (A1)
adjusted to have a solids content of 20 to 40 wt. % in the coating
composition to a substrate so that the dry film thickness is 1 to
15 .mu.m, and then applying an aqueous base coating composition
(A2) adjusted to have a solids content of 2 to 15 wt. % in the
coating composition to the uncured coating film so that the dry
film thickness is 0.1 to 5 .mu.m.
However, despite the recent demand for metallic luster like a
mirror-finished surface in which the 60.degree. gloss value is 130
or more, coating films formed by the coating method disclosed in
PTL 8 have insufficient metallic luster.
PTL 9 discloses a coating composition, wherein the specular gloss
of 20.degree. mirror reflection of a coated article is 300 or more,
and the normal reflectance in a visible light region is 40% or
more. However, PTL 9 is silent about the anti-water adhesion of the
coating film.
CITATION LIST
Patent Literature
PTL 1: JPS63-272544A PTL 2: JPH11-90318A PTL 3: JP2003-313500A PTL
4: JP2005-120249A PTL 5: JP2009-028690A PTL 6: JP2009-028693A PTL
7: JP2009-155537A PTL 8: JP2006-095522A PTL 9: JP5685044B
SUMMARY OF INVENTION
Technical Problem
An object of the present invention is to provide a method for
forming a multilayer coating film, whereby a metallic coating film
having excellent metallic luster and anti-water adhesion can be
formed.
Solution to Problem
One embodiment of the present invention provides a method for
forming a multilayer coating film by sequentially performing the
following steps (1) to (4):
(1) applying a colored coating composition (X) to a substrate to
form a colored coating film,
(2) applying an effect pigment dispersion (Y) to the colored
coating film formed in step (1) to form an effect coating film,
(3) applying a clear coating composition (Z) to the effect coating
film formed in step (2) to form a clear coating film, and
(4) heating the uncured colored coating film, the uncured effect
coating film, and the uncured clear coating film formed
respectively in steps (1) to (3) to simultaneously cure these three
coating films;
wherein the effect pigment dispersion (Y) contains water, a surface
modifier (A), a flake-effect pigment (B), and a viscosity modifier
(C),
the surface modifier (A) has a contact angle of 8 to 20.degree.
with respect to a previously degreased tin plate (produced by
Paltek Corporation), the contact angle being measured in such a
manner that a liquid that is a mixture of isopropanol, water, and
the surface modifier (A) at a ratio of 4.5/95/1 is adjusted to have
a viscosity of 150 mPas measured by a B-type viscometer at a rotor
rotational speed of 60 rpm at a temperature of 20.degree. C., 10
.mu.L of the liquid is added dropwise to the tin plate, and the
contact angle with respect to the tin plate is measured 10 seconds
after dropping, and
a film obtained by applying the effect pigment dispersion (Y) to a
dry film thickness of 0.2 .mu.m has a light transmittance at a
wavelength of 550 nm of 10 to 50%.
Advantageous Effects of Invention
According to the method for forming a multilayer coating film of
the present invention, a coating film having an appearance with
excellent metallic luster and anti-water adhesion is obtained.
DESCRIPTION OF EMBODIMENTS
1. Step (1)
Step (1) is to apply a colored coating composition (X) to a
substrate to form a colored coating film.
Substrate
Examples of the substrate used in the method for forming a
multilayer coating film of the present invention include metals,
such as iron, zinc, and aluminum; metal materials, such as alloys
containing these metals; molded products of these metals; molded
products of glass, plastic, foam, and the like. Degreasing
treatment or surface treatment can be suitably performed depending
on these materials to obtain substrates. Examples of the surface
treatment include phosphate treatment, chromate treatment,
composite oxide treatment, and the like. Furthermore, when the
material of the substrate is metal, it is preferable that an
undercoating film is formed on a surface-treated metal material
using a cationic electrodeposition coating composition or the like.
Moreover, when the material of the substrate is plastic, it is
preferable that a primer coating film is formed on a degreased
plastic material using a primer coating composition.
Colored Coating Composition (X)
As the colored coating composition (X), a known thermosetting
coating composition comprising a vehicle-forming resin, a pigment,
and a solvent, such as an organic solvent and/or water, as main
components can be specifically used. Examples of the thermosetting
coating composition include intermediate coating compositions, base
coating compositions, and the like.
Examples of the vehicle-forming resin used in the colored coating
composition (X) include thermosetting resins,
room-temperature-curable resins, and the like. However, in terms of
water resistance, chemical resistance, weather resistance, and the
like, thermosetting resins are preferably used. It is preferable to
use the vehicle-forming resin in combination with a base resin and
a crosslinking agent.
The base resin is preferably a resin that has excellent weather
resistance, transparency, and the like. Specific examples include
acrylic resins, polyester resins, epoxy resins, urethane resins,
and the like.
Examples of acrylic resins include resins obtained by
copolymerizing .alpha.,.beta.-ethylenically unsaturated carboxylic
acids, (meth)acrylic acid esters having a functional group, such as
a hydroxyl group, an amide group, or a methylol group, other
(meth)acrylic-acid esters, styrene, and the like.
Usable examples of polyester resins include those obtained by the
condensation reaction of polybasic acid, polyhydric alcohol, or
denatured oil, by a conventional method.
Examples of epoxy resins include epoxy ester resins obtained by a
method in which an epoxy ester is synthesized by the reaction of an
epoxy group and an unsaturated fatty acid, and an
.alpha.,.beta.-unsaturated acid is added to this unsaturated group;
or by a method in which the hydroxyl group of epoxy ester and a
polybasic acid, such as phthalic acid or trimellitic acid, are
esterified.
Examples of urethane resins include urethane resins whose molecular
weight is increased by reacting an acrylic resin, a polyester
resin, or an epoxy resin mentioned above with a dipolyisocyanate
compound.
The colored coating composition (X) may be an aqueous coating
composition or a solvent-based coating composition. However, in
terms of reducing the VOC of the coating composition, the colored
coating composition (X) is preferably an aqueous coating
composition. When the colored coating composition (X) is an aqueous
coating composition, the base resin can be made soluble in water or
dispersed in water by using a resin containing a hydrophilic group,
such as a carboxyl group, a hydroxyl group, a methylol group, an
amino group, a sulfonic acid group, or a polyoxyethylene bond, most
generally a carboxyl group, in an amount sufficient for making the
resin soluble in water or dispersed in water, and neutralizing the
hydrophilic group to form an alkali salt. The amount of the
hydrophilic group (e.g., a carboxyl group) used in this case is not
particularly limited, and can be suitably selected depending on the
degree of water solubilization or water dispersion. However, the
amount of the hydrophilic group is generally such that the acid
value is about 10 or more mgKOH/g, and preferably 30 to 200
mgKOH/g. Examples of the alkaline substance used in neutralization
include sodium hydroxide, amine compounds, and the like.
Moreover, dispersion of the above resin in water can be performed
by emulsion polymerization of the above monomer components in the
presence of a surfactant and a water-soluble resin. Furthermore,
the water dispersion can also be obtained by, for example,
dispersing the above resin in water in the presence of an
emulsifier. In the water dispersion, the base resin may not contain
the above hydrophilic group at all, or may contain the above
hydrophilic group in an amount less than the water-soluble
resin.
The crosslinking agent is used to crosslink and cure the base resin
by heating. Examples include amino resins, polyisocyanate compounds
(including unblocked polyisocyanate compounds and blocked
polyisocyanate compounds), epoxy-containing compounds,
carboxy-containing compounds, carbodiimide group-containing
compounds, hydrazide group-containing compounds, semicarbazide
group-containing compounds, and the like. Preferable among these
are amino resins reactive with a hydroxyl group, polyisocyanate
compounds, and carbodiimide group-containing compounds reactive
with a carboxyl group. These crosslinking agents can be used singly
or in a combination of two or more.
Specifically, amino resins obtained by condensation or
co-condensation of formaldehyde with melamine, benzoguanamine,
urea, or the like, or further etherification with a lower
monohydric alcohol, are suitably used. Further, a polyisocyanate
compound can also be suitably used.
The ratio of each component in the colored coating composition (X)
may be freely selected as required. However, in terms of water
resistance, finish, and the like, it is generally preferable that
the ratio of the base resin is 60 to 90 mass %, and particularly 70
to 85 mass %, based on the total mass of both components; and that
the ratio of the crosslinking agent is 10 to 40 mass %, and
particularly 15 to 30 mass %, based on the total mass of both
components.
The pigment provides color and substrate-masking properties to the
colored coating film formed from the colored coating composition
(X). By adjusting the type and amount of the pigment, the
brightness L* value of the coating film obtained from the colored
coating composition (X) can be adjusted within the range of 0.1 to
80, preferably 0.1 to 70, and more preferably 0.1 to 60. Examples
of the pigment include metallic pigments, rust preventive pigments,
coloring pigments, extender pigments, and the like. Of these,
coloring pigments are preferably used, and black pigments are more
preferably used in terms of obtaining a coating film with excellent
substrate-masking properties and metallic luster.
Pigments may be used in a suitable combination depending on light
transmittance, substrate-masking properties, desired color, and the
like. The amount thereof used is suitably an amount in which the
light transmittance of a cured coating film having a film thickness
of 15 .mu.m formed from the colored coating composition (X) at a
wavelength of 400 to 700 nm is 10% or less, and preferably 5% or
less, in terms of substrate-masking properties, weather resistance,
and the like.
The light transmittance of the coating film refers to spectral
transmittance measured by a recording spectrophotometer (Model
EPS-3T, produced by Hitachi, Ltd.) at a wavelength of 400 to 700 nm
using, as a sample, a coating film obtained by applying a coating
composition to a glass plate so that the cured coating film has a
predetermined film thickness, followed by curing, immersion in warm
water at 60 to 70.degree. C., removal of the coating film, and
drying. When there is a difference in the measured wavelengths (400
to 700 nm), the maximum value is used as light transmittance.
An organic solvent may also be used for the colored coating
composition (X), if necessary. Specifically, organic solvents
generally used for coating compositions can be used. Examples
include hydrocarbons, such as toluene, xylene, hexane, and heptane;
esters, such as ethyl acetate, butyl acetate, ethylene glycol
monomethyl ether acetate, diethylene glycol monoethyl ether
acetate, and diethylene glycol monobutyl acetate; ethers, such as
ethylene glycol monomethyl ether, ethylene glycol diethyl ether,
diethylene glycol monomethyl ether, and diethylene glycol dibutyl
ether; alcohols, such as butanol, propanol, octanol, cyclohexanol,
and diethylene glycol; ketones, such as methyl ethyl ketone, methyl
isobutyl ketone, cyclohexanone, and isophorone; and other organic
solvents. These can be used singly or in a combination of two or
more.
Among the above organic solvents, esters, ethers, alcohols, and
ketones are preferable in terms of solubility.
The cured film thickness of the colored coating film obtained from
the colored coating composition (X) is 15 .mu.m or more, preferably
15 to 30 .mu.m, and more preferably 15 to 25 .mu.m, in terms of
light transmittance, substrate-masking properties, metallic luster,
and the like.
Coating of the colored coating composition (X) can be performed by
a general method. When the colored coating composition (X) is an
aqueous coating composition, for example, deionized water and
optionally additives, such as a thickener and an antifoaming agent,
are added to the colored coating composition (X) so that the solids
content is adjusted to about 10 to 60 mass % and the viscosity is
adjusted to 200 to 5000 cps/6 rpm (B-type viscometer). Then, the
resultant is applied to the substrate surface by spray coating,
rotary atomization coating, or the like. An electrostatic charge
may be applied, if necessary, during coating.
The monochrome hiding film thickness of the colored coating
composition (X) is preferably 40 .mu.m or less, more preferably 5
to 35 .mu.m, and even more preferably 10 to 30 .mu.m, in terms of
color stability. In the present specification, the "monochrome
hiding film thickness" is a value obtained in the following manner.
The monochrome checkered hiding power test paper specified in 4.1.2
of JIS K5600-4-1 is attached to a steel plate. Then, the coating
composition is applied by inclined coating so that the film
thickness continuously varies, and dried or cured. The coating
surface is then visually observed under diffused daylight, and the
minimum film thickness in which the monochrome border of the
checker of the hiding power test paper disappears is measured by an
electromagnetic film thickness meter. The measured value is the
"monochrome hiding film thickness."
2. Step (2)
Step (2) is to apply an effect pigment dispersion (Y) to the
colored coating film formed in step (1) to form an effect coating
film.
It is preferable that a film obtained by applying the effect
pigment dispersion (Y) to a dry film thickness of 0.2 .mu.m have a
light transmittance at a wavelength of 550 nm of 10 to 50%, and
preferably 20 to 50%, because the coating film to be obtained has
excellent metallic luster and water resistance.
When the clear coating composition (Z) is a one-component clear
coating composition, the light transmittance at a wavelength of 550
nm of a film obtained by applying the effect pigment dispersion (Y)
to a dry film thickness of 0.2 .mu.m is 10 to 50%, preferably 15 to
50%, and more preferably 20 to 50%. When the light transmittance at
a wavelength of 550 nm is 10% or more, the coating film to be
obtained has excellent metallic luster, even though the dry film
thickness of the effect pigment dispersion (Y) is 0.2 .mu.m. When
the light transmittance at a wavelength of 550 nm is 50% or less,
the coating film to be obtained has excellent water resistance,
even though the dry film thickness of the effect pigment dispersion
(Y) is 0.2 .mu.m.
When the clear coating composition (Z) is a two-component clear
coating composition containing a hydroxy-containing resin and a
polyisocyanate compound, the light transmittance at a wavelength of
550 nm of a film obtained by applying the effect pigment dispersion
(Y) to a dry film thickness of 0.2 .mu.m is 20 to 50%, preferably
20 to 40%, and more preferably 20 to 30%. When the light
transmittance at a wavelength of 550 nm is 20% or more, the coating
film to be obtained has excellent metallic luster, even though the
dry film thickness of the effect pigment dispersion (Y) is 0.2
.mu.m. When the light transmittance at a wavelength of 550 nm is
50% or less, the coating film to be obtained has excellent water
resistance, even though the dry film thickness of the effect
pigment dispersion (Y) is 0.2 .mu.m.
The light transmittance refers to transmittance measured by a
recording spectrophotometer (Solid Spec 3700, produced by Shimadzu
Corp.) at a wavelength of 550 nm using a sample that is a coating
film obtained by applying the effect pigment dispersion (Y) to an
OHP sheet to a cured coating film thickness of 0.2 .mu.m, followed
by drying at 80.degree. C. for 3 minutes.
Effect Pigment Dispersion (Y)
The effect pigment dispersion (Y) contains water, a surface
modifier (A), a flake-effect pigment (B), and a viscosity modifier
(C).
Surface Modifier (A)
The surface modifier (A) is used to facilitate uniform orientation
of a flake-effect pigment (B), described later, dispersed in water
on the substrate when the effect pigment dispersion is applied to
the substrate.
The surface modifier (A) is not particularly limited, as long as it
has a contact angle of 8 to 20.degree., preferably 9 to 19.degree.,
and more preferably 10 to 18.degree., with respect to a previously
degreased tin plate (produced by Paltek Corporation), the contact
angle being measured in such a manner that a liquid that is a
mixture of isopropanol, water, and the surface modifier (A) at a
ratio of 4.5/95/1 is adjusted to have a viscosity of 150 mPas
measured by a B-type viscometer at a rotor rotational speed of 60
rpm at a temperature of 20.degree. C., 10 .mu.L of the liquid is
added dropwise to the tin plate, and the contact angle with respect
to the tin plate is measured 10 seconds after dropping.
Specifically, the viscosity is controlled by adding Acrysol ASE-60
(trade name, a polyacrylic acid-based viscosity modifier, produced
by The Dow Chemical Company, solids content: 28%) and
dimethylethanolamine.
The 4.5/95/1 ratio, which is the ratio of isopropanol/water/surface
modifier (A), corresponds to the component ratio of the effect
pigment dispersion (Y) for evaluating the surface modifier. The 150
mPas viscosity measured by a B-type viscometer at a rotor
rotational speed of 60 rpm is a normal value during coating to a
substrate. Moreover, the 8 to 20.degree. contact angle with respect
to the tin plate represents the wet spreading of liquid under
standard coating conditions. When the contact angle is 8.degree. or
more, the liquid is applied to a substrate without being overly
spread; whereas when the contact angle is 20.degree. or less, the
liquid is uniformly applied to a substrate without being overly
repelled.
Examples of the surface modifier (A) include silicone-based surface
modifiers, acrylic-based surface modifiers, vinyl-based surface
modifiers, and fluorine-based surface modifiers. These surface
modifiers can be used singly or in a combination of two or
more.
Examples of commercial products of the surface modifier (A) include
BYK series (produced by BYK-Chemie), Tego series (produced by
Evonik), Glanol series and Polyflow series (produced by Kyoeisha
Chemical Co., Ltd.), DISPARLON series (produced by Kusumoto
Chemicals, Ltd.), and the like.
The surface modifier (A) is preferably a silicone-based surface
modifier, in terms of the metallic luster, water resistance, and
the like, of the coating film to be obtained. Usable silicone-based
surface modifiers include polydimethylsiloxane and modified
silicone obtained by modifying polydimethylsiloxane. Examples of
modified silicone include polyether-modified silicone,
acrylic-modified silicone, polyester-modified silicone, and the
like.
The dynamic surface tension of the surface modifier (A) is
preferably 50 to 70 mN/m, more preferably 53 to 68 mN/m, and even
more preferably 55 to 65 mN/m. In the present specification, the
dynamic surface tension refers to a surface tension value measured
by the maximum bubble pressure method at a frequency of 10 Hz. The
dynamic surface tension was measured using a SITA measuring
apparatus (SITA t60, produced by EKO Instruments).
Moreover, the static surface tension of the surface modifier (A) is
preferably 15 to 30 mN/m, more preferably 18 to 27 mN/m, and even
more preferably 20 to 24 mN/m. In the present specification, the
static surface tension refers to a surface tension value measured
by the platinum ring method. The static surface tension was
measured using a surface tensiometer (DCAT 21, produced by EKO
Instruments).
Furthermore, the lamellar length of the surface modifier (A) is
preferably 6.0 to 9.0 mm, more preferably 6.5 to 8.5 mm, and even
more preferably 7.0 to 8.0 mm.
Flake-Effect Pigment (B)
Examples of the flake-effect pigment (B) in the effect pigment
dispersion (Y) include vapor-deposition metal flake pigments,
aluminum flake pigments, light interference pigments, and the like.
Of these, vapor-deposition metal flake pigments are preferred, in
terms of obtaining a coating film with excellent metallic
luster.
The vapor-deposition metal flake pigment is obtained by
vapor-depositing a metal film on a base material, removing the base
material, and then grinding the vapor-deposition metal film.
Examples of the base material include films and the like.
The material of the above metal is not particularly limited.
Examples include aluminum, gold, silver, copper, brass, titanium,
chromium, nickel, nickel chromium, stainless steel, and the like.
Of these, aluminum or chromium is particularly preferable, in terms
of easy availability, ease of handling, and the like. In the
present specification, a vapor-deposition metal flake pigment
obtained by vapor deposition of aluminum refers to a
"vapor-deposition aluminum flake pigment," and a vapor-deposition
metal flake pigment obtained by vapor deposition of chromium refers
to a "vapor-deposition chromium flake pigment."
Examples of commercial products that can be used as the
vapor-deposition aluminum flake pigment include "METALURE" series
(trade name, produced by ECKART), "Hydroshine WS" series (trade
name, produced by ECKART), "Decomet" series (trade name, produced
by Schlenk), "Metasheen" series (trade name, produced by BASF), and
the like.
Examples of commercial products that can be used as the
vapor-deposition chromium flake pigment include "Metalure Liquid
Black" series (trade name, produced by ECKART) and the like.
The average thickness of the vapor-deposition metal flake pigment
is preferably 0.01 to 1.0 .mu.m, and more preferably 0.015 to 0.1
.mu.m.
The average particle size (D50) of the vapor-deposition metal flake
pigment is preferably 1 to 50 .mu.m, and more preferably 5 to 20
.mu.m.
The surface of the vapor-deposition aluminum flake pigment is
preferably treated with silica, in terms of obtaining a coating
film with excellent storage stability and metallic luster.
Aluminum flake pigments are generally produced by grinding or
milling aluminum in a ball mill or an attritor mill in the presence
of a grinding liquid medium using a grinding aid. For coating
compositions, aluminum flake pigments having an average particle
size (D50) of about 1 to 50 .mu.m, particularly about 5 to 20
.mu.m, are generally used, in terms of the stability in the coating
composition, and the finish of the coating film to be formed. The
above-mentioned average particle size means a major axis. Usable
grinding aids include higher fatty acids, such as oleic acid,
stearic acid, isostearic acid, lauric acid, palmitic acid, and
myristic acid; as well as aliphatic amine, aliphatic amide, and
aliphatic alcohol. As the grinding liquid medium, an aliphatic
hydrocarbon, such as mineral spirit, is used.
Viscosity Modifier (C)
As the viscosity modifier (C) in the effect pigment dispersion (Y),
a known viscosity modifier can be used. Examples include
silica-based fine powder, mineral-based viscosity modifiers, barium
sulfate atomization powder, polyamide-based viscosity modifiers,
organic resin fine particle viscosity modifiers, diurea-based
viscosity modifiers, urethane association-type viscosity modifiers,
polyacrylic acid-based viscosity modifiers, which are acrylic
swelling-type, cellulose-based viscosity modifiers, and the like.
Of these, in terms of obtaining a coating film with excellent
metallic luster, it is particularly preferable to use a
mineral-based viscosity modifier, a polyacrylic acid-based
viscosity modifier, or a cellulose-based viscosity modifier.
Examples of mineral-based viscosity modifiers include swelling
laminar silicate that has a 2:1 type crystal structure. Specific
examples include smectite group clay minerals, such as natural or
synthetic montmorillonite, saponite, hectorite, stevensite,
beidellite, nontronite, bentonite, and laponite; swelling mica
group clay minerals, such as Na-type tetrasilicic fluorine mica,
Li-type tetrasilicic fluorine mica, Na salt-type fluorine
taeniolite, and Li-type fluorine taeniolite; and vermiculite; or
substitution products and derivatives thereof, or mixtures
thereof.
Examples of polyacrylic acid-based viscosity modifiers include
sodium polyacrylate, polyacrylic acid-(meth)acrylic acid ester
copolymers, and the like.
Examples of commercial products of the polyacrylic acid-based
viscosity modifier include "Primal ASE-60," "Primal TT615," and
"Primal RM5" (trade names, produced by The Dow Chemical Company);
"SN Thickener 613," "SN Thickener 618," "SN Thickener 630," "SN
Thickener 634," and "SN Thickener 636" (trade names, produced by
San Nopco Limited); and the like. The acid value of the solids
content of the polyacrylic acid-based viscosity modifier is 30 to
300 mgKOH/g, and preferably 80 to 280 mgKOH/g.
Examples of cellulose-based viscosity modifiers include
carboxymethylcellulose, methylcellulose, hydroxyethylcellulose,
hydroxyethylmethylcellulose, hydroxypropylmethylcellulose,
methylcellulose, cellulose nanofiber gel, and the like. Of these,
cellulose nanofiber gel is particularly preferable, because the
coating film to be obtained has excellent metallic luster. Examples
of commercial products thereof include "Rheocrysta" (trade name,
produced by DKS Co. Ltd.) and the like.
These viscosity modifiers can be used singly or in a suitable
combination of two or more.
Other Components
In particular, when the effect pigment dispersion (Y) contains an
aluminum pigment, it is preferable that the effect pigment
dispersion (Y) contain a phosphate group-containing resin, in terms
of the metallic luster and water resistance of the coating film to
be obtained.
The phosphate group-containing resin can be produced by, for
example, copolymerizing a phosphate group-containing polymerizable
unsaturated monomer and other polymerizable unsaturated monomers by
a known method, such as a solution-polymerization method. Examples
of the phosphate group-containing polymerizable unsaturated monomer
include acid phosphooxy ethyl(meth)acrylate, acid phosphooxy
propyl(meth)acrylate, a reaction product of glycidyl (meth)acrylate
and alkyl phosphoric acid, and the like. These may be used singly
or in a combination of two or more.
In the phosphate group-containing resin, when the above phosphate
group-containing polymerizable unsaturated monomer and another
polymerizable unsaturated monomer are copolymerized, the ratio of
each monomer used is such that the mass ratio of the former monomer
to the latter monomer is preferably about 1/99 to 40/60, more
preferably about 5/95 to 35/65, and even more preferably about
10/90 to 30/70.
The effect pigment dispersion (Y) may further suitably contain, if
necessary, an organic solvent, a pigment other than the
flake-effect pigment (B), a pigment dispersant, an antisettling
agent, an antifoaming agent, an ultraviolet absorber, a surface
modifier other than the surface modifier (A), or the like.
The effect pigment dispersion (Y) may contain a base resin and a
dispersion resin, in terms of the adhesion and storage stability of
the coating film to be obtained. However, the effects of the
present invention can be exhibited even if these resins are not
substantially contained.
Examples of the base resin include acrylic resins, polyester
resins, alkyd resins, urethane resins, and the like.
As the dispersion resin, existing dispersion resins, such as
acrylic resins, epoxy resins, polycarboxylic acid resins, and
polyester resins, can be used.
Crosslinkable Component (D)
The effect pigment dispersion (Y) may contain a crosslinkable
component (D), in terms of the anti-water adhesion of the coating
film to be obtained. In particular, when a clear coating
composition (Z), described later, does not contain the
cross-linking component (D), it is necessary for the effect pigment
dispersion (Y) to contain the crosslinkable component (D).
In the present specification, the crosslinkable component (D) is
selected from the group consisting of melamine, a melamine
derivative, (meth)acrylamide, a copolymer of N-methylol group- or
N-alkoxymethyl group-containing (meth)acrylamide, and a blocked or
unblocked polyisocyanate compound.
Examples of melamine derivatives include partially etherified or
fully etherified melamine resins produced by etherifying a part or
all of methylol groups in methylolated melamine with a C.sub.1-8
monohydric alcohol, such as methyl alcohol, ethyl alcohol, n-propyl
alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol,
2-ethylbutanol, or 2-ethylhexanol.
Examples of commercially available melamine derivatives include
Cymel 202, Cymel 232, Cymel 235, Cymel 238, Cymel 254, Cymel 266,
Cymel 267, Cymel 272, Cymel 285, Cymel 301, Cymel 303, Cymel 325,
Cymel 327, Cymel 350, Cymel 370, Cymel 701, Cymel 703, and Cymel
1141 (all produced by Nihon Cytec Industries Inc.); U-Van 20SE60,
U-Van 122, and U-Van 28-60 (all produced by Mitsui Chemicals,
Inc.); Super Beckamine J-820-60, Super Beckamine L-127-60, and
Super Beckamine G-821-60 (all produced by DIC); and the like.
The above melamine and melamine derivatives may be used singly or
in a combination of two or more.
Examples of the N-methylol group- or N-alkoxymethyl
group-containing (meth)acrylamide include (meth)acrylamides, such
as N-methylolacrylamide, N-methoxymethylacrylamide,
N-methoxybutylacrylamide, and N-butoxymethyl(meth)acrylamide.
The above (meth)acrylamide derivatives may be used singly or in a
combination of two or more.
The unblocked polyisocyanate compound is a compound having at least
two isocyanate groups per molecule. Examples include aliphatic
polyisocyanates, alicyclic polyisocyanates, aliphatic-aromatic
polyisocyanates, aromatic polyisocyanates, derivatives of these
polyisocyanates, and the like.
Examples of aliphatic polyisocyanates include aliphatic
diisocyanates, such as trimethylene diisocyanate, tetramethylene
diisocyanate, hexamethylene diisocyanate, pentamethylene
diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene
diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate,
2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid
diisocyanate, and 2,6-diisocyanatomethyl hexanoate (common name:
lysine diisocyanate); aliphatic triisocyanates, such as
2-isocyanatoethyl 2,6-diisocyanatohexanoate,
1,6-diisocyanato-3-isocyanatomethylhexane,
1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane,
1,8-diisocyanato-4-isocyanatomethyloctane,
1,3,6-triisocyanatohexane, and
2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane; and the
like.
Examples of alicyclic polyisocyanates include alicyclic
diisocyanates, such as 1,3-cyclopentene diisocyanate,
1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate,
3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common
name: isophorone diisocyanate), 4-methyl-1,3-cyclohexylene
diisocyanate (common name: hydrogenated TDI),
2-methyl-1,3-cyclohexylene diisocyanate, 1,3- or
1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated
xylylene diisocyanate) or mixtures thereof, and
methylenebis(4,1-cyclohexanediyl)diisocyanate (common name:
hydrogenated MDI), and norbornane diisocyanate; alicyclic
triisocyanates, such as 1,3,5-triisocyanatocyclohexane,
1,3,5-trimethylisocyanatocyclohexane,
2-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane,
2-(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo(2.2.1)heptane,
3-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane,
5-(2-isocyanatoethyl)-2-isocyanatomethy-3-(3-isocyanatopropyl)-bicyclo(2.-
2.1)heptane,
6-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2-
.2.1)heptane,
5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2-
.2.1)heptane, and
6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2-
.2.1)heptane; and the like.
Examples of aromatic-aliphatic polyisocyanates include
aromatic-aliphatic diisocyanates, such as
methylenebis(4,1-phenylene)diisocyanate (common name: MDI), 1,3- or
1,4-xylylene diisocyanate or mixtures thereof,
.omega.,.omega.'-diisocyanato-1,4-diethylbenzene, and 1,3- or
1,4-bis(1-isocyanato-1-methylethyl)benzene (common name:
tetramethylxylylene diisocyanate) or mixtures thereof;
aromatic-aliphatic triisocyanates, such as
1,3,5-triisocyanatomethylbenzene; and the like.
Examples of aromatic polyisocyanates include aromatic
diisocyanates, such as m-phenylene diisocyanate, p-phenylene
diisocyanate, 4,4'-diphenyldiisocyanate, 1,5-naphthalene
diisocyanate, 2,4-tolylene diisocyanate (common name: 2,4-TDI), or
2,6-tolylene diisocyanate (common name: 2,6-TDI) or mixtures
thereof, 4,4'-toluidine diisocyanate, and 4,4'-diphenylether
diisocyanate; aromatic triisocyanates, such as
triphenylmethane-4,4',4''-triisocyanate,
1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene;
aromatic tetraisocyanates, such as
4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate; and the like.
Examples of polyisocyanate derivatives include dimers, trimers,
biurets, allophanates, urethodiones, urethoimines, isocyanurates,
oxadiazinetriones, polymethylene polyphenyl polyisocyanates (crude
MDI, polymeric MDI), crude TDI, and the like, of the
above-mentioned polyisocyanates. These polyisocyanate derivatives
may be used singly or in a combination of two or more.
The above polyisocyanates and derivatives thereof may be used
singly or in a combination of two or more.
Among the aliphatic diisocyanates, hexamethylene diisocyanate
compounds are preferably used, and among the alicyclic
diisocyanates, 4,4'-methylenebis(cyclohexylisocyanate) is
preferably used. Of these, derivatives of hexamethylene
diisocyanate are particularly the most preferable, in terms of
adhesion, compatibility, and the like.
As the polyisocyanate compound, it is also possible to use a
prepolymer formed by reacting the polyisocyanate or a derivative
thereof with a compound having active hydrogen, such as hydroxy or
amino, and reactive to the polyisocyanate under conditions such
that the isocyanate groups are present in excess. Examples of the
compound reactive to the polyisocyanate include polyhydric
alcohols, low-molecular-weight polyester resins, amine, water, and
the like.
The above polyisocyanate compounds may be used singly or in a
combination of two or more.
The blocked polyisocyanate compound is a blocked polyisocyanate
compound in which some or all of the isocyanate groups of the above
polyisocyanate or a derivative thereof are blocked with a blocking
agent.
Examples of the blocking agents include phenol compounds, such as
phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl,
butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl
hydroxybenzoate; lactam compounds, such as .epsilon.-caprolactam,
.delta.-valerolactam, .gamma.-butyrolactam, and
.beta.-propiolactam; aliphatic alcohols, such as methanol, ethanol,
propyl alcohol, butyl alcohol, amyl alcohol, and lauryl alcohol;
ethers, such as ethylene glycol monomethyl ether, ethylene glycol
monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol
monomethyl ether, diethylene glycol monoethyl ether, propylene
glycol monomethyl ether, and methoxymethanol; alcohols, such as
benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate,
butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl
lactate, methylol urea, methylol melamine, diacetone alcohol,
2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate; oximes,
such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl
ketoxime, diacetyl monoxime, benzophenone oxime, and cyclohexane
oxime; active methylenes, such as dimethyl malonate, diethyl
malonate, ethyl acetoacetate, methyl acetoacetate, and
acetylacetone; mercaptans, such as butyl mercaptan, t-butyl
mercaptan, hexyl mercaptan, t-dodecyl mercaptan,
2-mercaptobenzothiazole, thiophenol, methylthiophenol, and
ethylthiophenol; acid amides, such as acetanilide, acetanisidide,
acetotoluide, acrylamide, methacrylamide, acetic acid amide,
stearic acid amide, and benzamide; imides, such as succinimide,
phthalimide, and maleimide; amines, such as diphenylamine,
phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole,
aniline, naphthylamine, butylamine, dibutylamine, and
butylphenylamine; imidazoles, such as imidazole and
2-ethylimidazole; ureas, such as urea, thiourea, ethylene urea,
ethylenethiourea, and diphenylurea; carbamate esters, such as
phenyl N-phenylcarbamate; imines, such as ethyleneimine and
propyleneimine; sulfites, such as sodium bisulfite and potassium
bisulfite; azole-based compounds; and the like. Examples of the
azole-based compounds include pyrazole or pyrazole derivatives,
such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole,
4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole,
4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole;
imidazole or imidazole derivatives, such as imidazole,
benzimidazole, 2-methylimidazole, 2-ethylimidazole, and
2-phenylimidazole; and imidazoline derivatives, such as
2-methylimidazoline and 2-phenylimidazoline.
When blocking is performed (a blocking agent is reacted), it can be
performed by adding a solvent, if necessary. As the solvent used in
the blocking reaction, a solvent that is not reactive with an
isocyanate group is preferably used. Examples include ketones, such
as acetone and methyl ethyl ketone; esters, such as ethyl acetate;
N-methyl-2-pyrrolidone (NMP); and like solvents.
The above blocked polyisocyanate compounds can be used singly or in
a combination of two or more.
When the effect pigment dispersion (Y) contains a crosslinkable
component (D), the content thereof as a solids content is
preferably within the range of 10 to 100 parts by mass, more
preferably 15 to 95 parts by mass, and even more preferably 20 to
100 parts by mass, based on 100 parts by mass of the solids content
of the flake-effect pigment (B) in the effect pigment dispersion
(Y), in terms of the anti-water adhesion of the coating film.
When the effect pigment dispersion (Y) contains a base resin and a
dispersion resin described above, and further contains a
crosslinkable component (D), the total amount as a solids content
of the base resin, the dispersion resin, and the crosslinkable
component (D) is, in terms of forming a coating film with metallic
luster, preferably within the range of 0.1 to 500 parts by mass,
more preferably 1 to 300 parts by mass, and even more preferably 10
to 100 parts by mass, based on 100 parts by mass of the solids
content of the flake-effect pigment (B) in the effect pigment
dispersion (Y), in terms of the anti-water adhesion of the coating
film.
When the effect pigment dispersion (Y) contains a base resin and/or
a crosslinkable component (D), the ratio of the flake-effect
pigment to the total amount of the base resin and the crosslinking
agent is preferably within the range of 1/1 to 100/1, more
preferably 3/1 to 50/1, and even more preferably 5/1 to 10/1, based
on the solids content mass.
Amount of Each Component in Effect Pigment Dispersion (Y)
The proportion (solids content mass) of water, the surface modifier
(A), the flake-effect pigment (B), and the viscosity modifier (C)
in the effect pigment dispersion (Y) is preferably within the
following range, in terms of obtaining a coating film with
excellent metallic luster.
The amount of each component based on 100 parts by mass of the
total amount of water, the surface modifier (A), the flake-effect
pigment (B), and the viscosity modifier (C) is as follows:
water: 70 to 99 parts by mass, preferably 80 to 99 parts by mass,
and more preferably 90 to 99 parts by mass;
surface modifier (A): 0.1 to 10 parts by mass, preferably 0.2 to 8
parts by mass, and more preferably 0.4 to 6 parts by mass:
flake-effect pigment (B): 0.05 to 3.0 parts by mass, preferably 0.2
to 1.5 parts by mass, and more preferably 0.3 to 0.6 parts by mass;
and
viscosity modifier (C): 0.1 to 26 parts by mass, preferably 0.5 to
10 parts by mass, and more preferably 1.0 to 5.0 parts by mass.
Contact Angle of Effect Pigment Dispersion (Y)
The contact angle of the effect pigment dispersion (Y) is 8 to
20.degree., and preferably 10 to 18.degree., in terms of obtaining
a coating film with excellent metallic luster. The contact angle
meter used in this case is CA-X150 (produced by Kyowa Chemical
Industry Co., Ltd.). The viscosity of the effect pigment dispersion
(Y) measured by a B-type viscometer at a rotor rotational speed of
60 rpm is adjusted to 150 mPas, 10 .mu.L is added dropwise to a
previously degreased tin plate (produced by Paltek Corporation),
and the viscosity is measured 10 seconds after dropping. The
measured value refers to the contact angle.
Step (2) of the present invention is to apply the effect pigment
dispersion (Y) to the above substrate to form an effect coating
film.
Coating of Effect Pigment Dispersion (Y)
The effect pigment dispersion (Y) is prepared by mixing and
dispersing the above components. In terms of obtaining a coating
film with excellent metallic luster, the solids content during
coating is preferably adjusted to 0.1 to 15 mass %, and more
preferably 0.2 to 5.0 mass %, based on the effect pigment
dispersion (Y).
The viscosity of the effect pigment dispersion (Y) at a temperature
of 20.degree. C. measured by a B-type viscometer at 60 rpm after 1
minute (also referred to as "the B60 value" in the present
specification) is preferably 60 to 1500 mPas, more preferably 60 to
1000 mPas, and even more preferably 60 to 500 mPas, in terms of
obtaining a coating film with excellent metallic luster. The
viscometer used in this case is a B-type viscometer (trade name:
LVDV-I, produced by Brookfield).
The effect pigment dispersion (Y) can be applied by a method such
as electrostatic spraying, air spray coating, or airless spray
coating. In the method for forming a multilayer coating film of the
present invention, rotary atomization type electrostatic spraying
is particularly preferable.
It is preferable that the effect coating film obtained by applying
the effect pigment dispersion (Y) is dried. The method of drying
the effect coating film is not particularly limited. For example, a
method that allow the coating film to stand at ordinary temperature
for 15 to 30 minutes, a method that performs preheating at a
temperature of 50 to 100.degree. C. for 30 seconds to 10 minutes,
or the like, can be used.
The film thickness 30 seconds after the effect pigment dispersion
(Y) is attached to the substrate is preferably 3 to 25 .mu.m, more
preferably 4 to 24 .mu.m, and even more preferably 5 to 23 .mu.m,
in terms of obtaining a coating film with excellent metallic
luster.
The thickness of the effect coating film, as dry film thickness, is
preferably 0.02 to 5.0 .mu.m, more preferably 0.02 to 4.0 .mu.m,
and even more preferably 0.02 to 3.5 .mu.m, in terms of obtaining a
coating film with excellent metallic luster.
In particular, when the flake-effect pigment (B) in the effect
pigment dispersion (Y) is a vapor-deposition metal-flake pigment,
the thickness of the effect coating film, as dry film thickness, is
preferably 0.01 to 1.0 .mu.m, and more preferably 0.01 to 0.5
.mu.m. For example, the thickness of the effect coating film, as
dry film thickness, is 0.01 or more and less than 0.5 .mu.m.
3. Step (3)
Step (3) is to apply a clear coating composition (Z) to the effect
coating film formed in step (2) to form a clear coating film.
Clear Coating Composition (Z)
The clear coating composition (Z) may be a one-component clear
coating composition containing a base resin and a curing agent, or
a two-component clear coating composition having a
hydroxy-containing resin and a polyisocyanate compound. The
polyisocyanate compound is as described in the "Effect pigment
dispersion (Y)" section.
Examples of combinations of a base resin and a curing agent in the
one-component clear coating composition include a
carboxy-containing resin and an epoxy-containing resin, a
hydroxy-containing resin and a blocked polyisocyanate compound, a
hydroxy-containing resin and a melamine resin, and the like. When a
one-component coating composition is used as the clear coating
composition (Z), the clear coating composition (Z) preferably
contains a crosslinkable component (D) in terms of the anti-water
adhesion of the coating film to be obtained. In particular, when
the effect pigment dispersion (Y) does not contain the
crosslinkable component (D), it is necessary that the clear coating
composition (Z) contain the crosslinkable component (D).
As the hydroxy-containing resin, conventionally known resins can be
used without limitation, as long as they are resins containing a
hydroxyl group. Examples of the hydroxy-containing resin include
hydroxy-containing acrylic resins, hydroxy-containing polyester
resins, hydroxy-containing polyether resins, hydroxy-containing
polyurethane resins, and the like; preferably hydroxy-containing
acrylic resins and hydroxy-containing polyester resins; and
particularly preferably hydroxy-containing acrylic resins.
The hydroxy value of the hydroxy-containing acrylic resin is
preferably within the range of 80 to 200 mgKOH/g, and more
preferably 100 to 180 mgKOH/g. When the hydroxy value is 80 mgKOH/g
or more, the crosslinking density is high, and thus the scratch
resistance is sufficient. Further, when the hydroxy value is 200
mgKOH/g or less, the water resistance of the coating film is
maintained.
The weight average molecular weight of the hydroxy-containing
acrylic resin is preferably within the range of 2500 to 40000, and
more preferably 5000 to 30000. When the weight average molecular
weight is 2500 or more, the coating film performance, such as acid
resistance, is excellent. When the weight average molecular weight
is 40000 or less, the smoothness of the coating film is maintained,
and thus the finish is excellent.
In the present specification, the weight average molecular weight
refers to a value calculated from a chromatogram measured by gel
permeation chromatography based on the molecular weight of standard
polystyrene. For the gel permeation chromatography, "HLC8120GPC"
(produced by Tosoh Corporation) was used. The measurement was
conducted using four columns: "TSKgel G-4000HXL," "TSKgel
G-3000HXL," "TSKgel G-2500HXL," and "TSKgel G-2000HXL" (trade
names, all produced by Tosoh Corporation) under the following
conditions: mobile phase: tetrahydrofuran, measuring temperature:
40.degree. C., flow rate: 1 cc/min, and detector: RI.
The glass transition temperature of the hydroxy-containing acrylic
resin is -40.degree. C. to 20.degree. C., and particularly
preferably -30.degree. C. to 10.degree. C. When the glass
transition temperature is -40.degree. C. or more, the coating film
hardness is sufficient. When the glass transition temperature is
20.degree. C. or less, the coating surface smoothness of the
coating film is maintained.
As the crosslinkable component (D), those described in the "Effect
Pigment Dispersion (Y)" section can be used.
When the clear coating composition (Z) contains the crosslinkable
component (D), the content thereof as a solids content is
preferably within the range of 5 to 25 parts by mass, more
preferably 10 to 20 parts by mass, and even more preferably 15 to
18 parts by mass, based on 100 parts by mass of the resin solids
content of the clear coating composition (Z), in terms of the
anti-water adhesion of the coating film.
The clear coating composition (Z) may suitably contain additives,
such as solvents (e.g., water and organic solvents), curing
catalysts, antifoaming agents, and ultraviolet absorbers, if
necessary.
The clear coating composition (Z) may suitably contain a coloring
pigment within a range that does not impair transparency. As the
coloring pigment, conventionally known pigments for ink or coating
compositions can be used singly or in a combination of two or more.
The amount thereof to be added may be suitably determined, but is
preferably 30 parts by weight or less, and more preferably 0.01 to
10 parts by weight, based on 100 parts by mass of the
vehicle-forming resin composition in the clear coating composition
(Z).
The form of the clear coating composition (Z) is not particularly
limited. The clear coating composition (Z) is generally used as an
organic solvent-based coating composition. Examples of the organic
solvent used in this case include various organic solvents for
coating compositions, such as aromatic or aliphatic hydrocarbon
solvents, ester solvents, ketone solvents, ether solvents, and the
like. As the organic solvent used herein, the one used in the
preparation of the hydroxy-containing resin may be used as is, or
other organic solvents may be further suitably added.
The clear coating composition (Z) can be prepared by mixing a
hydroxy-containing resin, a polyisocyanate compound, and optionally
a curing catalyst, a pigment, various resins, an ultraviolet
absorber, a light stabilizer, an organic solvent, and the like, by
a known method.
The solids concentration of the clear coating composition (Z) is
preferably about 30 to 70 mass %, and more preferably about 40 to
60 mass %.
The clear coating composition (Z) is applied to the effect coating
film. The coating of the clear coating composition (Z) is not
particularly limited, and the same method as those for the colored
coating composition (X) and the effect pigment dispersion (Y) may
be used. For example, the clear coating composition (Z) can be
applied by a coating method, such as air spray coating, airless
spray coating, rotary atomization coating, or curtain coating. In
these coating methods, an electrostatic charge may be applied, if
necessary. Among these, rotary atomization coating using an
electrostatic charge is preferable. The coating amount of the clear
coating composition (Z) is generally preferably an amount in which
the cured film thickness is about 10 to 50 .mu.m.
Moreover, when the clear coating composition (Z) is applied, it is
preferable to suitably adjust the viscosity of the clear coating
composition (Z) within a viscosity range suitable for the coating
method. For example, for rotary atomization coating using an
electrostatic charge, it is preferable to suitably adjust the
viscosity of the clear coating composition (Z) within a range of
about 15 to 60 seconds measured by a Ford cup No. 4 viscometer at
20.degree. C. using a solvent, such as an organic solvent.
After the clear coating composition (Z) is applied to form a clear
coating film, for example, preheating can be performed at a
temperature of about 50 to 80.degree. C. for about 3 to 10 minutes
so as to promote the vaporization of volatile components.
4. Step (4)
Step (4) is to heat the uncured colored coating film, the uncured
effect coating film, and the uncured clear coating film formed in
steps (1) to (3) to simultaneously cure these three coating
films.
Heating can be performed by a known means. For example, a drying
furnace, such as a hot-blast stove, an electric furnace, or an
infrared beam heating furnace, can be used.
The heating temperature is preferably within the range of 70 to
150.degree. C., and more preferably 80 to 140.degree. C.
The heating time is not particularly limited, but is preferably
within the range of 10 to 40 minutes, and more preferably 20 to 30
minutes.
EXAMPLES
The present invention is described in more detail below with
reference to Examples and Comparative Examples. However, the
present invention is not limited only to these Examples. "Part(s)"
and "%" are both based on mass.
Test Example 1
1. Surface Modifier (A)
Table 1 shows the properties of surface modifiers (A) used in the
production of effect pigment dispersions (Y) described later.
(A-1) to (A-4) are all commercially available surface modifiers.
(A-1) is a silicone-based surface modifier, (A-2) is a mixture of a
surface modifier of an amphiphilic oligomer and a silicone-based
surface modifier, (A-3) is polyether-based siloxane, and (A-4) is a
fluorine-modified acrylic surface modifier.
TABLE-US-00001 TABLE 1 Name (A-1) (A-2) (A-3) (A-4) Contact angle
[.degree.] 13 12 14 39 (Note 1) Dynamic surface 63.9 51.5 68.7 71.3
tension [mN/m] Static surface 22.2 21.6 21.9 38.8 tension [mN/m]
Lamellar 7.45 7.40 7.46 7.55 length [mm] (Note 1): A contact angle
with respect to a previously degreased tin plate (produced by
Paltek Corporation) measured in such a manner that a liquid
prepared by mixing isopropanol, water, and the surface modifier (A)
at a ratio of 4.5/95/1 was adjusted to have a viscosity of 100 mPa
s measured by a B-type viscometer at a rotor rotational speed of 60
rpm at a temperature of 20.degree. C., 10 .mu.L of the liquid was
added dropwise to the tin plate, and the contact angle with respect
to the tin plate was measured by a contact angle meter (CA-X150,
trade name, produced by Kyowa Chemical Industry Co., Ltd.) 10
seconds after dropping.
2. Production of Phosphate Group-Containing Resin
A mixed solvent of 27.5 parts of methoxy propanol and 27.5 parts of
isobutanol was placed in a reaction vessel equipped with a
thermometer, a thermostat, a stirrer, a reflux condenser, and a
dropping funnel, and heated to 110.degree. C. While the temperature
was maintained at 110.degree. C., 121.5 parts of a mixture
comprising 25 parts of styrene, 27.5 parts of n-butyl methacrylate,
20 parts of branched higher alkyl acrylate (trade name: "Isostearyl
Acrylate," produced by Osaka Organic Chemical Industry Ltd.), 7.5
parts of 4-hydroxybutyl acrylate, 15 parts of a phosphate
group-containing polymerizable monomer described below, 12.5 parts
of 2-methacryloyloxyethyl acid phosphate, 10 parts of isobutanol,
and 4 parts of tert-butylperoxy octanoate was added dropwise to the
above mixed solvent over 4 hours. Further, a mixture comprising 0.5
parts of tert-butylperoxy octanoate and 20 parts of isopropanol was
added dropwise for 1 hour. Then, the resultant was stirred and aged
for 1 hour, thereby obtaining a phosphate group-containing resin
solution having a solids content of 50%. The phosphate
group-containing resin had an acid value of 83 mgKOH/g, a hydroxy
value of 29 mgKOH/g, and a weight average molecular weight of
10,000.
Phosphate group-containing polymerizable monomer: 57.5 parts of
monobutyl phosphoric acid and 41 parts of isobutanol were placed in
a reaction vessel equipped with a thermometer, a thermostat, a
stirrer, a reflux condenser, and a dropping funnel, and heated to
90.degree. C. After 42.5 parts of glycidyl methacrylate was added
dropwise over 2 hours, the mixture was stirred and aged for 1 hour.
Thereafter, 59 parts of isopropanol was added, thereby obtaining a
phosphate group-containing polymerizable monomer solution having a
solids content of 50%. The acid value of the obtained monomer was
285 mgKOH/g.
3. Production of Effect Pigment Dispersion (Y)
Production Example 1
92 parts of distilled water, 1 part of the surface modifier (A-2),
5 parts (solids content of 0.5 parts) of Hydroshine WS-3004 (an
aqueous vapor-deposition aluminum flake pigment, produced by
Eckart, solids content: 10%; internal solvent: isopropanol, average
particle size D50: 13 .mu.m, thickness: 0.05 .mu.m; the surface was
treated with silica), 1.7 parts (solids content of 0.48 parts) of
Acrysol ASE-60 (a polyacrylic acid-based viscosity modifier,
produced by The Dow Chemical Company, solids content: 28%), and
0.17 parts of dimethylethanolamine were blended, stirred, and
mixed, thereby preparing an effect pigment dispersion (Y-1).
Production Examples 2 to 15
Effect pigment dispersions (Y-2) to (Y-16) were obtained in the
same manner as in Production Example 1, except that the
formulations shown in Table 2 were used.
TABLE-US-00002 TABLE 2 Numerical values in parentheses in the table
are solids contents. Production Example No. 1 2 3 4 5 6 7 8 Name of
effect pigment dispersion Y-1 Y-2 Y-3 Y-4 Y-5 Y-6 Y-7 Y-8
Formulation Water Distilled water 92 92 91 91 94 91 93 92 Surface
Surface modifier A-1 1 0.8 1 1 1 1 modifier (A) A-2 1 A-3 1 Surface
modifier A-4 other than surface modifier (A) Effect
Vapor-deposition WS3004 5 5 5 5 3 6 5 5 pigment aluminum flake
(0.5) (0.5) (0.5) (0.5) (0.3) (0.6) (0.5) (0.5) (B) Viscosity
ASE-60 1.7 1.7 1.7 1.7 1.7 1.7 1.2 0.9 modifier (0.48) (0.48)
(0.48) (0.48) (0.48) (0.48) (0.34) (0.25) (C) Dimethylethanolamine
0.17 0.17 0.17 0.17 0.17 0.17 0.15 0.75 Performance Light
transmittance at a wavelength of 20 25 30 25 50 20 25 25 550 nm
when the film thickness of the effect coating film is 0.2 .mu.m (%)
Coating composition viscosity 150 150 150 150 150 150 60 1500 B60
value (mPa s) Concentration of effect pigment (B) in 0.5 0.5 0.5
0.5 0.5 0.6 0.5 0.5 coating composition (%) Production Example No.
9 10 11 12 13 14 15 16 Name of effect pigment dispersion Y-9 Y-10
Y-11 Y-12 Y-13 Y-14 Y-15 Y-16 Formulation Water Distilled water 96
74 88 93 92 92 90 90 Surface Surface modifier A-1 1 1 10 0.1 1 1 1
modifier (A) A-2 A-3 Surface modifier A-4 1 other than surface
modifier (A) Effect Vapor-deposition WS3004 0.75 24 5 5 5 5 7.3 7.3
pigment aluminum flake (0.075) (2.4) (0.5) (0.5) (0.5) (0.5) (0.73)
(0.73) (B) Viscosity ASE-60 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.0
modifier (0.48) (0.48) (0.48) (0.48) (0.48) (0.48) (0.48) (0.28)
(C) Dimethylethanolamine 0.17 0.17 0.17 0.17 0.17 0.17 0.17 0.8
Phosphate group-containing resin 0.9 (0.45) Performance Light
transmittance at a wavelength of 25 25 25 25 25 55 95 25 550 nm
when the film thickness of the effect coating film is 0.2 .mu.m (%)
Coating composition viscosity 150 150 150 150 150 150 150 1600 B60
value (mPa s) Concentration of effect pigment (B) in 0.075 2.4 0.5
0.5 0.5 0.5 0.73 0.73 coating composition (%)
4. Preparation of Substrate Production of Substrate 1
A cationic electrodeposition coating composition "Elecron 9400HB"
(trade name, produced by Kansai Paint Co., Ltd., an amine-modified
epoxy resin-based cationic resin containing a blocked
polyisocyanate compound as a curing agent) was applied by
electrodeposition to a degreased and zinc phosphate-treated steel
plate (JISG3141, size: 400.times.300.times.0.8 mm) to a film
thickness of 20 .mu.m when cured. The resulting film was heated at
170.degree. C. for 20 minutes to be cured by crosslinking, thereby
obtaining a substrate 1.
Production of Substrate 2
A primer "Soflex 1000" (trade name, produced by Kansai Paint Co.,
Ltd., a polyolefin-containing electrically conductive organic
solvent-based coating composition) was applied to an ABS plate
(black, degreased) by air spray coating to a dry film thickness of
15 .mu.m. The resulting film was heated at 80.degree. C. for 30
minutes to be cured, thereby obtaining a substrate 2.
5. Preparation of Test Plate
Example 1
A colored coating composition (X-1) "WP-522H N-2.0" (trade name,
produced by Kansai Paint Co., Ltd., a polyester resin-based aqueous
intermediate coating composition, L* value of the coating film to
be obtained: 20) was applied to the substrate 1 to a cured film
thickness of 20 .mu.m by electrostatic spraying using a rotary
atomization-type bell-shaped coating device. After the resulting
film was allowed to stand for 3 minutes, preheating was performed
at 80.degree. C. for 3 minutes. Further, the effect pigment
dispersion (Y-1) produced as described above was adjusted to have a
coating composition viscosity shown in Table 2, and applied to a
dry coating film thickness of 0.1 .mu.m using a robot bell
(produced by ABB) under the conditions in which the booth
temperature was 23.degree. C. and the humidity was 68%. The
resultant was then allowed to stand at 80.degree. C. for 3 minutes.
Subsequently, the dried coating surface was coated with a clear
coating composition (Z-1) "KINO6500" (trade name, produced by
Kansai Paint Co., Ltd., a hydroxy/isocyanate curable acrylic
resin/urethane resin-based two-component organic solvent-based
coating composition) to a dry coating film thickness of 25 to 35
.mu.m using a robot bell (produced by ABB) under the conditions in
which the booth temperature was 23.degree. C. and the humidity was
68%. After coating, the resultant was allowed to stand at room
temperature for 15 minutes, and then heated in a hot air
circulation-type dryer at 140.degree. C. for 30 minutes to
simultaneously dry the multilayer coating films, thereby obtaining
a test plate.
The film thickness of the dry coating film shown in Table 3 was
calculated from the following formula. The same applies to the
following Examples.
x=sc/sg/S*10000
x: film thickness [.mu.m]
sc: coating solids content [g]
sg: coating film specific gravity [g/cm.sup.3]
S: evaluation area of coating solids content [cm.sup.2]
Examples 2 to 15 and Comparative Examples 1 to 4
Test plates were obtained in the same manner as in Example 1,
except that the substrates and coating compositions shown in Table
3 were used.
The clear coating composition (Z-2) in the table is "KINO1210"
(trade name: Kansai Paint Co., Ltd., an acid/epoxy curable acrylic
resin-based one-component organic solvent-based coating
composition).
6. Evaluation of Coating Film
The appearance and performance of the coating film of each test
plate obtained in the above manner were evaluated. Table 3 shows
the results.
Evaluation of Appearance
The coating film appearance was evaluated by graininess, anti-water
adhesion, specular gloss (60.degree. gloss), and visual
observation.
Graininess
The graininess was evaluated as a hi-light graininess value
(hereinafter abbreviated as the "HG value"). The HG value is a
parameter of micro-brilliance obtained by the microscopic
observation of a coating surface, and indicates the graininess in
the highlight. The HG value is calculated as follows. First, the
coating surface is photographed with a CCD camera at a light
incidence angle of 15.degree. and a receiving angle of 0.degree.,
and the obtained digital image data (two-dimensional brilliance
distribution data) is subjected to two-dimensional Fourier
transformation to obtain a power spectrum image. Subsequently, only
the spatial frequency area corresponding to graininess is extracted
from the power spectrum image, and the obtained measurement
parameter is converted to an HG value from 0 to 100 that has a
linear relation with graininess. An HG value of 0 indicates no
graininess of the effect pigment at all, and an HG value of 100
indicates the highest possible graininess of the effect
pigment.
The graininess HG is preferably 10 to 40, in terms of the denseness
of the metallic coating film.
Anti-Water Adhesion
Each test plate was immersed in warm water at 80.degree. C. for 5
hours. After the test plate was removed from the water, cross-cuts
reaching the substrate were made in the multilayer coating film of
the test plate using a cutter knife to form a grid of 100 squares
(2 mm.times.2 mm). Subsequently, adhesive cellophane tape was
applied to the surface of the grid portion, and the tape was peeled
off rapidly at 20.degree. C. Then, the condition of squares
remaining was checked, and anti-water adhesion was evaluated
according to the following criteria. "Pass" is regarded as
acceptance.
Pass: 100 squares of the coating film remained, and no small
edge-chipping of the coating film occurred at the edge of the cut
made by the cutter knife.
Fail: The remaining number of squares of the coating film was 99 or
less.
Specular Gloss (60.degree. Gloss)
The 60.degree. gloss value of the test plates obtained above was
measured using a gloss meter (micro-TRI-gloss, produced by
BYK-Gardner). A numerical value of 130 or more is regarded as
acceptance.
When the 60-degree specular gloss of a multilayer coating film
obtained by forming an effect coating film on a colored coating
film, and further forming a coating film thereon is 150 to 240
degrees, it is preferable in terms of high glossiness.
Visual Feeling of Metal
The test plates obtained above were each observed outdoor on a fine
day while changing the angle of the test plate against outdoor
light, and graininess and the luminance difference (flip-flop
property: FF property) between the highlight region and the shade
region were evaluated. Less graininess and a higher flip-flop
property indicate that the coating film has excellent metal tone.
The evaluation was conducted on a five-grade scale by 2 designers
and 3 engineers (total: 5 persons) who had been engaged in color
development for 3 years or more, and the average value was
employed.
5: Reflection of sunlight is very strong, and the blue sky is
reflected on the coated plate. Graininess is very small and the FF
property is very high.
4: Reflection of sunlight is strong. Graininess is very small and
the flip-flop property is very high.
3: Reflection of sunlight is strong. Graininess is small and the
flip-flop property is high.
2: Reflection of sunlight is weak. Graininess is large and the
flip-flop property is low.
1: Reflection of sunlight is weak. Graininess is very large and the
FF property is very low.
TABLE-US-00003 TABLE 3 Examples 1 2 3 4 5 6 7 8 9 10 Name of
substrate 1 1 1 1 1 1 1 1 1 1 Name of colored coating composition
(X) X-1 X-1 X-1 X-1 X-1 X-1 X-1 X-1 X-1 X-1 Name of effect
dispersion (Y) Y-1 Y-2 Y-3 Y-4 Y-5 Y-6 Y-7 Y-8 Y-9 Y-10 Name of
clear coating composition (Z) Z-1 Z-1 Z-1 Z-1 Z-1 Z-1 Z-1 Z-1 Z-1
Z-1 Dry film thickness .mu.m 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 1.3
0.04 Coating film Graininess (HG, micro-brilliance) 28 28 32 32 33
26 28 36 38 36 performance Anti-water adhesion (80.degree. C.
.times. 5 h) Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass
60.degree. gloss 141 142 135 141 134 141 142 132 135 136 Visual
feeling of metal 4 5 3 5 3 4 5 3 3 4 Examples Comparative Examples
11 12 13 14 15 16 1 2 3 4 Name of substrate 1 1 1 1 1 2 1 1 1 1
Name of colored coating composition (X) X-1 X-1 X-1 X-1 X-1 X-1 X-1
X-1 X-1 X-1 Name of effect dispersion (Y) Y-10 Y-9 Y-11 Y-12 Y-13
Y-2 Y-14 Y-15 Y-16 Y-2 Name of clear coating composition (Z) Z-1
Z-1 Z-1 Z-1 Z-1 Z-1 Z-1 Z-1 Z-1 Z-2 Dry film thickness .mu.m 0.025
1.6 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Coating film Graininess (HG,
micro-brilliance) 38 40 28 44 30 25 50 40 46 28 performance
Anti-water adhesion (80.degree. C. .times. 5 h) Pass Pass Pass Pass
Pass Pass Pass Fail Pass Fail 60.degree. gloss 138 135 140 138 139
140 120 130 125 140 Visual feeling of metal 4 4 5 3 4 5 1 2 1 5
Test Example 2
In the following experiments, the same points as Test Example 1 are
omitted, and different points are described.
1. Surface Modifier (A)
The surface modifiers (A) used herein were the same surface
modifiers (A-1) to (A-4) of Table 1 used in Test Example 1.
2. Production of Effect Pigment Dispersion (Y)
Production Example 1B
92 parts of distilled water, 1 part of the surface modifier (A-1)
(Note 1), 5 parts (solids content of 0.5 parts) of Hydroshine
WS-3004 (trade name, an aqueous vapor-deposition aluminum flake
pigment, produced by Eckart, solids content: 10%, internal solvent:
isopropanol, average particle size D50: 13 .mu.m, thickness: 0.05
.mu.m; the surface was treated with silica), 1.23 parts (solids
content of 0.15 parts) of Cymel 325 (trade name, methyl-etherified
melamine resin, produced by Nihon Cytec Industries Inc., solids
content: 80%), 1.8 parts (solids content of 0.49 parts) of Acrysol
ASE-60 (a polyacrylic acid-based viscosity modifier, produced by
The Dow Chemical Company, solids content: 28%), and 0.18 parts of
dimethylethanolamine were blended, stirred, and mixed, thereby
obtaining an effect pigment dispersion (Y-1B).
Production Examples 2B to 16B
Effect pigment dispersions (Y-2B) to (Y-16B) were obtained in the
same manner as in Production Example 1B, except that the
formulations shown in Table 4 were used.
The details of the components shown in the table are as
follows.
"Imprafix 2794 XP": trade name, produced by Covestro AG, a blocked
aliphatic polyisocyanate compound, solids content: 38%
"Diyanal HR517": trade name, produced by Mitsubishi Rayon Co.,
Ltd., acrylic resin containing N-butoxymethylacrylamide as a
polymerizable component, solids content: 50%
"Rheocrysta": trade name, a cellulose-based viscosity modifier
(cellulose nanofiber), produced by Dai-Ichi Kogyo Seiyaku Co.,
Ltd., solids content: 2%
TABLE-US-00004 TABLE 4 Numerical values in parentheses in the table
are solids contents. Production Example No. 1B 2B 3B 4B 5B 6B 7B 8B
Name of effect pigment dispersion Y-1B Y-2B Y-3B Y-4B Y-5B Y-6B
Y-7B Y-8B Formulation Water Distilled water 92 92 92 92 92 92 92 92
Surface Surface modifier (A) A-1 1 1 1 1 1 1 1 1 modifier A-2 A-3
Surface modifier other than A-4 surface modifier (A) Effect
Vapor-deposition aluminum WS3004 5 5 5 5 3 6 2 6.5 pigment (B)
flake (0.5) (0.5) (0.5) (0.5) (0.3) (0.6) (0.2) (0.65)
Crosslinkable Melamine resin Cymel 325 0.23 component (0.15)
Blocked isocyanate Imprafix 0.33 compound 2796 (0.15) Acrylic resin
containing N- Diyanal 0.63 0.21 2.1 0.63 0.63 butoxyacrylamide
HR517 (0.15) (0.05) (0.5) (0.15) (0.15) Viscosity ASE-60 1.8 1.8
1.8 1.8 1.8 1.8 1.8 1.8 modifier (C) (0.49) (0.49) (0.49) (0.49)
(0.49) (0.49) (0.49) (0.49) Rheocrysta Dimethylethanolamine 0.18
0.18 0.18 0.18 0.18 0.18 0.18 0.18 Performance Light transmittance
at a wavelength of 550 nm when the 25 25 25 25 25 25 50 10 film
thickness of the effect coating film is 0.2 .mu.m (%) Coating
composition viscosity 150 150 150 150 150 150 150 150 B60 value
(mPa s) Concentration of effect pigment (B) in coating 0.5 0.5 0.5
0.5 0.5 0.6 0.39 1.23 composition (%) Production Example No. 9B 10B
11B 12B 13B 14B 15B 16B Name of effect pigment dispersion Y-9B
Y-10B Y-11B Y-12B Y-13B Y-14B Y-15B Y-16B Formulation Water
Distilled water 92 92 92 92 92 92 90 90 Surface Surface modifier
(A) A-1 1 1 1 1 1 modifier A-2 1 A-3 1 Surface modifier other than
A-4 1 surface modifier (A) Effect Vapor-deposition aluminum WS3004
5 5 5 5 3 6 1.4 8.5 pigment (B) flake (0.5) (0.5) (0.5) (0.5) (0.3)
(0.6) (0.14) (0.85) Crosslinkable Melamine resin Cymel 325 0.23
component (0.15) Blocked isocyanate Imprafix 0.33 compound 2796
(0.15) Acrylic resin containing N- Diyanal 0.63 0.63 0.63 0.63 0.63
0.63 0.63 butoxyacrylamide HR517 (0.15) (0.15) (0.15) (0.15) (0.15)
(0.15) (0.15)- Viscosity ASE-60 1.2 11.4 1.8 1.8 1.8 1.7 1.0
modifier (C) (0.34) (3.2) (0.49) (0.49) (0.49) (0.48) (0.28)
Rheocrysta 24.5 (0.49) Dimethylethanolamine 0.15 0.23 0.18 0.18
0.18 0.18 0.18 Performance Light transmittance at a wavelength of
550 nm when the 25 25 25 25 25 75 60 5 film thickness of the effect
coating film is 0.2 .mu.m (%) Coating composition viscosity 60 1500
150 150 150 150 150 150 B60 value (mPa s) Concentration of effect
pigment (B) in coating 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 composition
(%)
3. Preparation of Substrate
A substrate 1 was produced according to "4. Preparation of
Substrate" in Test Example 1.
4. Preparation of Test Plate
Example 1B
A colored coating composition (X-1) "WP-522H N-2.0" (trade name,
produced by Kansai Paint Co., Ltd., a polyester resin-based aqueous
intermediate coating composition, L* value of the coating film to
be obtained: 20) was applied to the substrate 1 to a cured film
thickness of 20 .mu.m by electrostatic spraying using a rotary
atomization-type bell-shaped coating device. After the resulting
film was allowed to stand for 3 minutes, preheating was performed
at 80.degree. C. for 3 minutes. Further, an effect pigment
dispersion (Y-1B) produced as described above was adjusted to have
a coating composition viscosity shown in Table 4, and applied to a
dry coating film thickness of 0.1 .mu.m using a robot bell
(produced by ABB) under the conditions in which the booth
temperature was 23.degree. C. and the humidity was 68%. The
resultant was then allowed to stand at 80.degree. C. for 3 minutes.
Subsequently, the dried coating surface was coated with a clear
coating composition (Z-1B) "KINO1210" (trade name, Kansai Paint
Co., Ltd., a carboxy-containing resin/epoxy-containing resin
curable one-component organic solvent-based coating composition) to
a dry coating film thickness of 25 to 35 .mu.m using a robot bell
(produced by ABB) under the conditions in which the booth
temperature was 23.degree. C. and the humidity was 68%. After
coating, the resultant was allowed to stand at room temperature for
15 minutes, and then heated in a hot air circulation-type dryer at
140.degree. C. for 30 minutes to simultaneously dry the multilayer
coating films, thereby obtaining a test plate.
The film thickness of the dry coating film shown in Table 5 was
calculated from the following formula. The same applies to the
following Examples.
x=sc/sg/S*10000
x: film thickness [.mu.m]
sc: coating solids content [g]
sg: coating film specific gravity [g/cm.sup.3]
S: evaluation area of coating solids content [cm.sup.2]
Examples 2B to 18B and Comparative Examples 1B to 6B
Test plates were obtained in the same manner as in Example 1B,
except that the substrates and coating compositions shown in Table
5 were used.
The clear coating compositions (Z-2B) to (Z-9B) in the table are as
follows.
TABLE-US-00005 TABLE 5 Examples 1B 2B 3B 4B 5B 6B 7B 8B 9B 10B 11B
12B Name of substrate 1 1 1 1 1 1 1 1 1 1 1 1 Name of effect
dispersion (Y) Y-1B Y-2B Y-3B Y-5B Y-6B Y-7B Y-8B Y-9B Y-10B Y-11B
Y-12B Y-13B Dry film thickness of effect coating film (.mu.m) 0.2
0.2 0.2 0.2 0.2 0.1 0.3 0.2 0.2 0.2 0.2 0.2 Name of dear coating
composition (Z) Z-1B Z-1B Z-1B Z-1B Z-1B Z-1B Z-1B Z-1B Z-1B Z-1B
Z-1B Z-1B Coating film Graininess (HG, micro-brilliance) 30 30 30
26 40 40 28 28 40 25 30 30 performance Anti-water adhesion
(80.degree. C. .times. 5 h) Pass Pass Pass Pass Pass Pass Pass Pass
Pass Pass Pass Pass Anti-water adhesion after exposure Pass Pass
Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass to severe weather
* 60.degree. gloss 140 140 140 145 135 145 130 145 135 160 140 140
Visual feeling of metal 5 5 5 5 4 4 4 5 4 5 5 5 Examples
Comparative Examples 13B 14B 15B 16B 17B 18B 1B 2B 38 4B 5B 6B Name
of substrate 1 1 1 1 1 1 1 1 1 1 1 1 Name of effect dispersion (Y)
Y-4B Y-4B Y-4B Y-3B Y-4B Y-4B Y-14B Y-15B Y-16B Y-4B Y-4B Y-4B Dry
film thickness of effect coating film (.mu.m) 0.2 0.2 0.2 0.2 0.2
0.2 0.2 0.1 0.5 0.2 0.2 0.2 Name of dear coating composition (Z)
Z-2B Z-3B Z-4B Z-5B Z-6B Z-7B Z-1B Z-1B Z-1B Z-1B Z-8B Z-9B Coating
film Graininess (HG, micro-brilliance) 30 30 30 30 27 40 50 50 33
28 26 50 performance Anti-water adhesion (80.degree. C. .times. 5
h) Pass Pass Pass Pass Pass Pass Pass Pass Fail Fail Fail Pass
Anti-water adhesion after exposure Pass Pass Pass Pass Pass Pass
Pass Pass Fail Fail Fail Pass to severe weather * 60.degree. gloss
140 140 140 140 143 133 110 145 125 142 145 125 Visual feeling of
metal 5 5 5 5 5 4 1 1 2 5 5 2
(Z-2B): a one-component clear coating composition obtained by
adding 10 parts by mass of "Cymel 325" to "KINO1210" based on 100
parts by mass of the resin solids content contained in the
"KINO1210"
(Z-3B): a one-component clear coating composition obtained by
adding 10 parts by mass of "Imprafix2794XP" to "KINO1210" based on
100 parts by mass of the resin solids content contained in the
"KINO1210"
(Z-4B): a one-component clear coating composition obtained by
adding 10 parts by mass of "Diyanal HR517" to "KINO1210" based on
100 parts by mass of the resin solids content contained in the
"KINO1210"
(Z-5B): "TC-71": trade name, produced by Kansai Paint Co., Ltd., a
hydroxy-containing resin/melamine resin curing one-component
organic solvent-based coating composition
(Z-6B): a one-component clear coating composition obtained by
adding 5 parts by mass of "Diyanal HR517" to "KINO1210" based on
100 parts by mass of the resin solids content contained in the
"KINO1210"
(Z-7B): a one-component clear coating composition obtained by
adding 20 parts by mass of "Diyanal HR517" to "KINO1210" based on
100 parts by mass of the resin solids content contained in the
"KINO1210"
(Z-8B): a one-component clear coating composition obtained by
adding 2 parts by mass of "Diyanal HR517" to "KINO1210" based on
100 parts by mass of the resin solids content contained in the
"KINO1210"
(Z-9B): a one-component clear coating composition obtained by
adding 30 parts by mass of "Diyanal HR517" to "KINO1210" based on
100 parts by mass of the resin solids content contained in the
"KINO1210"
5. Evaluation of Coating Film
The appearance and performance of the coating film of each test
plate obtained in the above manner were evaluated for the same
items as in "6. Evaluation of Coating Film" of Test Example 1.
Table 5 shows the results. The anti-water adhesion after exposure
to severe weather was evaluated as described below.
Anti-Water Adhesion after Exposure to Severe Weather
Each test plate was subjected to the following conditions for 2
hours per cycle, including irradiation with a xenon arc lamp for 1
hour and 42 minutes and raining for 18 minutes, using a super xenon
weatherometer (trade name, produced by Suga Test Instruments Co.,
Ltd.) specified in JIS B 7754. This cycle was repeated for 2000
hours. Thereafter, the test plates were each immersed in water at
40.degree. C. for 10 days. After removing each test plate from the
water, the condition of squares remaining was checked in the same
manner as described above regarding anti-water adhesion, and
anti-water adhesion was evaluated.
Pass: 100 squares of the coating film remained, and no small
edge-chipping of the coating film occurred at the edge of the cut
made by the cutter knife.
Fail: The remaining number of squares of the coating film was 99 or
less.
The embodiments and Examples of the present invention are described
in detail above. However, the present invention is not limited to
the above-mentioned embodiments, and various modifications can be
made based on the technical idea of the present invention.
Furthermore, the present invention can also employ the following
structures.
[1] A method for forming a multilayer coating film by sequentially
performing the following steps (1) to (4):
(1) applying a colored coating composition (X) to a substrate to
form a colored coating film,
(2) applying an effect pigment dispersion (Y) to the colored
coating film formed in step (1) to form an effect coating film,
(3) applying a clear coating composition (Z) to the effect coating
film formed in step (2) to form a clear coating film, and
(4) heating the uncured colored coating film, the uncured effect
coating film, and the uncured clear coating film formed
respectively in steps (1) to (3) to simultaneously cure these three
coating films;
wherein the effect pigment dispersion (Y) contains water, a surface
modifier (A), a flake-effect pigment (B), and a viscosity modifier
(C),
the surface modifier (A) has a contact angle of 8 to 20.degree.
with respect to a previously degreased tin plate (produced by
Paltek Corporation), the contact angle being measured in such a
manner that a liquid that is a mixture of isopropanol, water, and
the surface modifier (A) at a ratio of 4.5/95/1 is adjusted to have
a viscosity of 150 mPas measured by a B-type viscometer at a rotor
rotational speed of 60 rpm at a temperature of 20.degree. C., 10
.mu.L of the liquid is added dropwise to the tin plate, and the
contact angle with respect to the tin plate is measured 10 seconds
after dropping, and
a film obtained by applying the effect pigment dispersion (Y) to a
dry film thickness of 0.2 .mu.m has a light transmittance at a
wavelength of 550 nm of 10 to 50%.
[2] The method for forming a multilayer coating film according to
[1], wherein the clear coating composition (Z) is a one-component
clear coating composition; and
the effect pigment dispersion (Y) and/or the clear coating
composition (Z) contains at least one crosslinkable component (D)
selected from the group consisting of melamine, a melamine
derivative, (meth)acrylamide, an N-methylol group- or
N-alkoxymethyl group-containing (meth)acrylamide copolymer, and a
blocked or unblocked polyisocyanate compound,
when the effect pigment dispersion (Y) contains the crosslinkable
component (D), the content thereof as a solids content is within a
range of 10 to 100 parts by mass based on 100 parts by mass of the
solids content of the effect pigment in the effect pigment
dispersion (Y), and
when the clear coating composition (Z) contains the crosslinkable
component (D), the content thereof as a solids content is within a
range of 5 to 25 parts by mass based on 100 parts by mass of the
resin solids content of the clear coating composition (Z).
[3] The method for forming a multilayer coating film according to
[1], wherein the clear coating composition (Z) is a two-component
clear coating composition containing a hydroxy-containing resin and
a polyisocyanate compound.
[4] The method for forming a multilayer coating film according to
any one of [1] to [3], wherein the effect pigment dispersion (Y)
has a viscosity (B60) of 60 to 1500 mPas measured using a B-type
viscometer at a rotor rotational speed of 60 rpm at a temperature
of 20.degree. C.
[5] The method for forming a multilayer coating film according to
any one of [1] to [4], wherein the surface modifier (A) is a
silicone-based surface modifier.
[6] The method for forming a multilayer coating film according to
any one of [1] to [5], wherein the surface modifier (A) has a
dynamic surface tension of 50 to 70 mN/m.
[7] The method for forming a multilayer coating film according to
any one of [1] to [6], wherein the flake-effect pigment (B) is
contained in the effect pigment dispersion (Y) in an amount of 0.05
to 3.0 parts by mass, based on 100 parts by mass of the total
amount of water, the surface modifier (A), the flake-effect pigment
(B), and the viscosity modifier (C).
[8] The method for forming a multilayer coating film according to
any one of [1] to [7], wherein the effect coating film has a dry
film thickness of 0.02 to 5.0 .mu.m.
[9] The method for forming a multilayer coating film according to
any one of [1] to [7], wherein the effect coating film has a dry
film thickness of 0.01 to 1.0 .mu.m.
[10] The method for forming a multilayer coating film according to
any one of [1] to [9], wherein the clear coating composition (Z)
contains a carboxy-containing resin and an epoxy-containing
resin.
[11] The method for forming a multilayer coating film according to
any one of [1] to [10], wherein the clear coating composition (Z)
contains a hydroxy-containing resin and a melamine resin.
INDUSTRIAL APPLICABILITY
The method for forming a multilayer coating film of the present
invention can be applied to various industrial products,
particularly interior and exterior panels of automobile bodies, and
automobile components.
* * * * *